The third generation partnership project (3GPP) has lately initiated the Long Term Evolution (LTE) program to bring new technology, new network architecture, new configuration, and new applications and services to the wireless cellular network in order to provide improved spectral efficiency and faster user experiences.
In LTE, the tracking area (TA) concept replaces the universal mobile telecommunications system (UMTS) routing area/location area (RA/LA) and UMTS terrestrial radio access network registration area (URA) concepts to simplify the mobile area tracking operations and to reduce the overhead caused by the area updates a wireless transmit/receive unit (WTRU) has to perform. When a WTRU is in the LTE_IDLE state, it is typically not transmitting or receiving any packets. Because the WTRU is not in active communication with a base station or an enhanced Node B (eNB), its location may not be exactly known. A TA represents an area in which the WTRU was last registered, and it is necessary to page the WTRU in the TA to locate the WTRU in a particular cell. A TA update (TAU) is generated when the WTRU crosses the boundary from one TA to another TA.
In WTRU idle mode, the TA concept also includes RA updates (RAU) and LA updates (LAU) or combined RAU/LAU. The current LTE system has defined two TA operational schemes: the “multiple-TA registration” scheme and the “overlapping TA” scheme.
In the “multiple-TA” scheme, an LTE cell belongs to only one TA, but a WTRU can be assigned with more than one TA. If one WTRU is assigned to multiple TAs, the WTRU does not need to perform TAUs when it crosses the boundaries between assigned TAs.
In the “overlapping TA” scheme, one cell can be assigned to multiple TAs (broadcast in system information) and one WTRU is assigned only to one TA. In the overlapped cell, the WTRU does not have to perform a TAU if its assigned TA is in the TA list of the overlapped cell.
Consideration has been given to allocating TAs to reduce the number of TAUs and the consequent signaling overhead to the system. The arrangement and assignment of TAs in the LTE network affects the idle mode paging operation because the WTRU paging is performed by cells in all the assigned TAs. Additionally, in the multiple-TA list scheme, a WTRU may be allocated more than one TA. In the LTE_IDLE state, the network is aware of the WTRU only at a TA level. This means that, for paging and other purposes, the network can only contact the WTRU over all assigned TAs, which may unnecessarily increase the paging load. Further, the criteria and methods used in allocating multiple TAs to a WTRU are unclear.
Recently, there has also been considerable interest regarding “femto-cells”. These are cells of a short-range base station that may be deployed in a home or in certain public places (e.g., underground malls, train stations, etc.) to provide cellular coverage in areas that may not be accessible to macro-cells or to provide differentiated charging to users when they are accessing these cells. Such cells are referred to as femto-cells, Home Node B (HNB) cells, Home e-Node B (HeNB) cells or, most commonly, Closed Subscriber Group (CSG) cells.
It would therefore be beneficial to provide a method and apparatus that can provide the network with mobility and positioning information to assist in allocating TAs and also help achieve the best possible balance for the LTE system load between the operations of system paging and the TAUs.